1. Field of the Invention
This invention pertains to lighting fixtures featuring compact fluorescent lamps. More specifically, the invention is directed to apparatus and methods that improve ventilation for controlling the temperature of ballasts and lamps in compact fluorescent light fixtures. In such compact fluorescent light fixtures, sometimes referred to as “luminaires,” a plurality of compact fluorescent lamps is arranged inside a dome structure. The compact fluorescent lamps are powered through ballasts. Luminaires of this type are used in various installations such as factories, gymnasiums, sports arenas, large stores and warehouse buildings, as well as other structures and outdoor applications.
2. Description of Related Art
Incandescent and strip lamp fluorescent lighting fixtures are used in many applications and environments. For certain installations, typically large bay installations, dome style fixtures that are arranged in a grid pattern above an area to be lighted have replaced incandescent and strip lamp fixtures. Early adaptations of the dome style fixtures incorporated high intensity discharge lamps.
The use of luminaires designed for compact fluorescent lamps has become a viable alternative to high intensity discharge lamp fixtures. An early adaptation of compact fluorescent lamps is shown in U.S. Pat. Re. No. 36,414, “Lighting Apparatus,” Jerold A. Tickner, herein incorporated by reference. Also herein incorporated by reference is U.S. Pat. No. 6,905,226 for “Compact Fluorescent Light Fixture” to Tickner, et al. and U.S. Application Publication No. US-2006-0232984-A1 of K. Schuknecht for “Compact Fluorescent Lamp Fixture Ventilation Method and Apparatus.” A data sheet entitled “LX-Series Starliter” of Sportlite, Inc. related to high-bay luminaires is also incorporated by reference herein.
The high intensity discharge lamp fixtures being superseded are commonly mercury vapor, metal halide, and high and low pressure sodium lamps of high wattage. Compact fluorescent lamps in luminaires designed to replace these high intensity discharge lamp fixtures can be significantly more energy efficient and have other benefits as well. For instance, mercury vapor, metal halide, and high and low pressure sodium lamps take time to start, turn on and get up to full lumen output. Once such high intensity discharge lamps are turned on and operating it is preferable to leave the lamps on. On the other hand, an advantage over the high intensity discharge lamps is that the compact fluorescent lamps start and turn on quickly and may be switched on and off with relative frequency in a short time span. Thus, in a warehouse situation for instance, where compact fluorescent lamps are installed, the lamps can be turned off as workers leave the warehouse room for a short period of time. If, however, the warehouse room is lighted using high intensity discharge lamps such as mercury vapor, metal halide, and high and low pressure sodium lamps, it is not practical to turn such fixtures off since, if they need to be turned back on in a short time, not only is the energy needed to turn the fixtures back on significant, but these type of fixtures are slow to start thus preventing quick full light availability in a room.
Multiple ballast compact fluorescent lamps are easily step dimmed by selecting the number of ballasts and/or lamps that are turned on or off. The idea in step dimming is that some but not all of the lamps in a luminaire are turned off to lower the light output in steps rather than having the luminaire only being able to be on or off. Step dimming gives more light output flexibility. In at least one embodiment, a fluorescent fixture will have a single ballast connected to two fluorescent lamps. In a luminaire used to light a large area there may be multiple ballasts, for instance, more than one ballast, and multiple lamps, for instance more than two lamps, supported in each luminaire. To step dim a multi ballast and multi lamp luminaire a first ballast will be shut off to shut down lamps associated with that ballast. If further dimming is desired then another ballast will be shut off and the lamps connected to that ballast would be shut down. Several ballasts can be shut down at once, that is, it is possible but not necessary, to shut down only one ballast at a time. Step dimming assumes that the luminaire being step dimmed has multiple ballasts and lamps.
Compact fluorescent lamps operate at peak light output efficiency when each of the several lamps of each luminaire is operating within an optimum temperature range. In actual installations the air temperature around a lamp will increase depending on the level of cooling available. Thus it is desirable to develop apparatus and luminaire ventilation procedures to provide ventilation for the lamps in a luminaire to minimize heat build up in the vicinity of the lamp. In many cases this means that the lamps, and the ballasts as discussed below, are run as cool as possible since it will be more likely than not that the lamps will tend to run hotter, rather than cooler, in the luminaire environment than they do in open air. To reduce the complexity and length of the Detailed Specification, and to fully establish the state of the art in certain areas of technology, Applicant herein expressly incorporates by reference the following article: “Compact Fluorescent Lamps: What You Should Know,” D. W. Finn and M. J. Ouellette, National Research Council Canada, Institute for Research in Construction, available from the internet as of Jan. 5, 2007.